Gas pumping unit for oil wells

ABSTRACT

A pumping unit for oil wells, operating independently from conventional AIB rod pumps, which allows regulated gas extraction to keep the gas pressure constant inside the well and thus allowing the extraction of oil without the inconveniences of traditional pumping systems.

BACKGROUND OF THE INVENTION 1. Priority Claim

This application is a claims priority of Argentina Patent Application No. P 20170101354, filed May 19, 2017, the entire content of which is incorporated herein by reference.

2. Field of the Invention

The present invention relates to the field of machinery, arrangements and devices used in the oil industry, and more particularly it refers to a gas extracting and transferring unit for oil wells that allows reducing pressure in the well annulus depending on the well gas contribution, thus increasing the production of fluid from it. It is emphasized that, this gas pumping unit is completely independent from the systems commonly used for oil extraction, such as, for example, AIB (Independent Pumping Unit, for its abbreviation in Spanish) rod pumps, PCP, electro-submersible pumps, “PLUNGER LIFT” type pumps, etc., and in turn, it allows programming the required pressure in the well.

3. Description of the Prior Art

AIB rod pumps are well known in the oil industry, and are known to allow carrying out mechanical extraction of crude oil from oil wells. Rod pumps are commonly used in many oilfields, and depending on the size of the pump, 5 to more than 50 m3 of a mixture of crude oil and water can generally be produced in 24 hours. The size of the pump is also determined by the depth and weight of the crude oil to be extracted, wherein a deeper extraction requires more energy to move greater lengths of fluid column. A connecting rod-crank mechanism converts the motor rotary motion into a reciprocating vertical movement that moves the pump rod, and produces the typical pitch movement. Thus, the AIB rod pump allows the extraction of crude oil from wells.

As mentioned above, crude oil is accompanied by water and gas in the oilfield. However, the gas in the well can be a major problem for oil extraction. This can occur due to excessive gas pressure inside the well, more particularly in the annulus space between the casing and the pipe. The presence of excessive gas pressure significantly decreases oil production. As a result of the above, some arrangements have been developed that allow extracting the gas from the well annulus to reduce pressure and allow the normal production of crude oil. Currently, beam-rocker compressors are used in mechanical pumping for the transfer of gas, which are mounted and operated in conjunction with the AIB rod pumps, using a large piston and the extraction of gas depending on the number of strokes performed by the AIB.

However, although the use of beam-rocker compressors has proved to be practical in the field of the art, they have drawbacks that limit oil production. One of these drawbacks is the dependence on the movement of the head of the AIB to carry out the extraction of gas, so if compressor requires some type of maintenance, first the AIB should be stopped to carry out said maintenance, which entails losses of time and production. Also, although the gas pressure may vary in the well annulus, conventional compressors constantly extract equal amounts of gas in each stroke, so gas pressure inside the well can vary significantly affecting positively or negatively the production of oil.

By virtue of the above, it would be very convenient to have a new arrangement, device, machinery or means that may allow extraction of gas from the oil well without affecting the conditions of production of crude oil, allowing in turn an adequate extraction of gas according to pressures existing in the well.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a pumping unit for oil wells that allows gas extraction independently from the AIB rod pumps.

It is still another object of the present invention to provide a pumping unit that allows maintaining a constant gas pressure in the well, since it has a pressure switch, pressure transmitter and frequency converter that controls the speed of the piston as a function of the gas flow rate to be extracted.

It is also another object of the present invention to provide a pumping unit that, owing to its structural configuration, has a longer useful life and efficiency of the pumping unit due to minor maintenance and repairs

It is another object of the present invention to provide a gas pumping unit for oil wells that make it possible for pressure in the well to be programmable.

It is still another object of the present invention to provide a gas pumping unit for oil wells comprising at least one compressor cylinder having at least one gas inlet in connection with the well, at least one gas outlet, one pivoting lower end and a double-acting piston whose drive shaft is connected to a drive motor, which can be an electric, hydraulic or combustion motor, said drive motor being connected to a pressure transmitter operatively connected to a pressure switch which is in turn operatively connected to the well.

BRIEF DESCRIPTION OF THE DRAWINGS

For greater clarity and understanding of the object of the present invention, it has been illustrated in several figures, in which the invention has been represented in one of the preferred embodiments, all by way of example, wherein:

FIG. 1 shows an exemplary schematic view of the gas pumping unit for oil wells according to the present invention, wherein it has been illustrated, merely by way of example, in connection with the corresponding parts installed in the well.

FIG. 2 shows a perspective view of the gas pumping unit for oil wells according to the present invention; and

FIGS. 3 and 4 show a sectional view of the gas pumping unit according to the present invention, wherein the direction of advancement of the piston can be observed allowing gas entry and simultaneous compression/discharge thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures, it is seen that the invention consists of a new gas pumping unit for oil wells which is an unit independent from the AIB rod pumps that allows regulated extraction of gas to keep the gas pressure constant inside the well and thus allow the extraction of oil without any inconvenience. For exemplary purposes and to further improve the understanding of the present invention, FIG. 1 illustrates the pumping unit in connection with the respective parts of the well. As mentioned above, as it is an exemplary scheme, both the separation distances and the dimensions of the illustrated components have been illustrated disproportionately, it being understood that this is not a limitation for the invention and that in practice it correctly adapts to the demands of the place.

Thus, and according to FIGS. 1 to 4, the pumping unit for oil wells of the present invention is indicated by the general reference 1 and comprises at least one compressor cylinder 2 having an upper part 3 on which an upper sealing cover 4 is mounted and a lower part 5 on which a lower sealing cover 6 is mounted, both covers 4 and 6 being fixed to the cylinder 2 by respective bolts, pins or similar fixing elements. Likewise, said compressor cylinder 2 comprises an upper gas cylinder inlet/outlet mouth 7 provided in the upper part 3 and a lower gas cylinder inlet/outlet mouth 8 provided in the lower part 5.

Internally, the compressor cylinder 2 comprises a double-acting piston 9 whose drive shaft 10 passes through the upper cover 4 and has a proximal end that has a connection element 11 provided with a bearing 12 on which a connecting shaft 13 is fixed, said connecting shaft 13 allowing the connection between said driving shaft 10 and a respective connecting rod 14 which is connected to a drive motor 15-reducer 16 by means of the shaft 17 of the latter. The drive motor 10 may be a combustion, hydraulic or electric drive motor, but it is preferably an electric motor which is operatively connected to a pressure switch 18 by a pressure transmitter 41 which is used to control the speed of said motor-reducer, the pressure switch 18 being used to set or establish the start/stop pressure and being operatively connected to the well, more particularly to the annulus space between the casing and the extraction pipe. In this way, the pressure in the well can be programmable without any inconvenience, this not being possible by any of the conventional devices of the prior art since they operate with the beam pump stroke and there is no way of being able to program the pressure required in the well.

The pressure transmitter 41 measures the pressure in the annulus and regulates the rotational revolution of the motor so that the piston moves at a greater or lower speed inside the compressor cylinder. This allows the extraction of gas in accordance with gas pressure existing inside the annulus. By way of example, but not limiting the invention, if the gas pressure existing within the annulus space exceeds the maximum pressure limit necessary to allow the extraction of oil, the pressure transmitter 41 sends a signal to the variable speed drive of the motor so that it rotates at higher revolutions and thus generating a greater speed in the piston movement, consequently extracting a greater amount of gas from the annulus in order to reduce the pressure existing in it. Likewise, the use of the pressure transmitter makes it possible to know the pressure in the annulus and to maintain the ideal pressure therein on a constant basis. In turn, owing to the pressure switch arrangement and the pressure transmitter, the required pressure inside the well can be programmable according to the operating conditions of the moment.

For its part, the connecting rod 14 provides an eccentric movement rectilinear to the drive shaft 10 of the piston 9 which moves longitudinally inside the compressor cylinder 2 to allow the entry of gas as well as, simultaneously, its compression and discharge. When said driving shaft 10 performs a rectilinear eccentric movement, it causes the compressor cylinder 2 to pivot in a tilting manner. To facilitate the tilting movement of the compressor cylinder 2, a pivoting lower end is provided which comprises a lower arm 19 provided with a bearing 20 through which a shaft 21 passes whose ends are fixed to respective lateral support plates (not shown) provided with bearings (not shown) and which are mounted on a frame (not shown) that supports the general structure of the unit of the invention. In this way, pivoting from the lower end is allowed accompanying the eccentric rectilinear movement of the drive shaft 10 and the tilting movement of the cylinder 2.

On the other hand, the invention comprises at least one main gas inlet 22 in connection with the well annulus and at least one main gas outlet 23 in connection with the gas production line and/or related reservoirs. Although, according to the direction illustrated in FIGS. 1 to 4, it has been indicated that the main gas inlet 22 is on the right, while the main gas outlet is on the left, this does not imply that the invention is limited to said configuration, but other arrangements can be considered and used without any inconvenience.

The main gas inlet 22 bifurcates and projects into a lower gas inlet 24 which is in connection with the lower gas cylinder inlet/outlet 8 of the lower part 5 of the cylinder 2 through a unidirectional check valve 25, and in a upper gas inlet 26 which is connected to the upper gas cylinder inlet/outlet 7 of the upper part 3 of the compressor cylinder 2 by another unidirectional check valve 27. In turn, the present invention has a lower gas outlet 28 which is connected to the lower gas cylinder inlet/outlet 8 by a unidirectional check valve 29 and an upper gas outlet 30 which is connected to the upper gas cylinder inlet/outlet 7 through another unidirectional check valve 31, both gas outlets 28 and 30 extending and being connected to the main gas outlet 23.

It is noted that projections and bifurcations mentioned above include tubes or pipes 32 as well as bends 33, shut-off valves, connectors, flanges, seals, stuffing boxes, etc., as best illustrated in FIGS. 1 to 4. Likewise, the main gas inlet 22 and the main gas outlet 23 have connectors 34 and are connected to the well and reservoir/production line respectively by means of a conduit 40 or conduits such as duct(s), pipe(s), hose(s) or the like. More particularly, and in accordance with FIG. 1, it can be seen that the main gas inlet 22 is in connection with a suction gas outlet 35 from which the gas of the well annulus comes, while said main outlet of gas 23 is in connection with a discharge gas inlet 36 which is projected towards the gas production line and/or related reservoirs. Also, in said FIG. 1 some components of those parts that are usually used in wells have been illustrated for exemplary and helping purposes for a better understanding of the present invention. Wherein, said components that are illustrated are the “casing” 37, pipe 38 and rod 39 among many others.

By way of example, but not limiting the invention, according to what is illustrated in FIG. 3, when the piston 9 moves upwards, the gas entering through the main gas inlet 22 is projected entering the cylinder 2 through of the lower gas inlet 24—lower gas inlet/outlet 8. Simultaneously, it can be seen that the gas that was previously inside the cylinder is compressed and discharged through the upper gas cylinder inlet/outlet 7, passing through the upper gas outlet 30 and finally being discharged through the main gas outlet 23.

On the other hand, FIG. 4, when the piston 9 moves down, the gas entering through the main gas inlet 22 is projected entering the cylinder 2 through the upper gas inlet 26—upper gas cylinder inlet/outlet 7.

Simultaneously, it can be seen that the gas that previously entered the cylinder, according to FIG. 3, is compressed and discharged through the lower gas cylinder inlet/outlet 8, passing through the lower gas outlet 28, and finally being discharged through the main gas outlet 23.

The use of the unidirectional check valves 25, 27, 29 and 31, define the direction of gas flow for both the entry and exit from/to the cylinder, thus avoiding the possible return of the gas. Likewise, both the direction of gas circulation and the main gas inlet and outlet are not limited to what has been described above, but can be adapted for having other configurations without any inconvenience.

By way of example, but not limiting the invention, some tables are attached showing the results obtained by the pumping unit of the invention:

Discharge Flow Tables:

thousands of cubic feet of gas under standard conditions per day (MSCF/D−thousand standard cubic feet per day)

8.73×10⁻⁵ ×D ² ×L×RPM×Q=PS;  Calculation equation:

Calculations should be made with absolute pressures.

Piston diameter 6″ P Revolution per minute Piston net suction (RPM) in gear box outlet stroke (inches) (psig) 10 20 30 10 0 4.7 9.42 14.1 5 6.3 12.6 18.8 10 7.8 15.7 23.5 15 9.4 18.8 28.3 20 11.0 21.9 32.9 25 12.6 25.1 37.7 30 14.1 28.3 42.4

Piston diameter 8″ P Revolution per minute Piston net suction (RPM) in gear box outlet stroke (inches ) (psig) 10 20 30 16 0 13.4 26.8 40.2 5 17.9 35.8 53.6 10 22.3 44.7 67.0 15 26.8 53.6 80.4 20 31.2 62.5 93.7 25 35.7 71.5 107.2 30 40.2 80.4 120.7

Torque Table:

(depending on pressure difference, diameter and effective stroke of the piston) Newton-meter

#N−m=4.44×10⁻² ×D ² ×L(Pd−Ps);  Calculation equation:

wherein, pressure difference: Discharge pressure−Suction pressure.

Pressure difference Piston diameter: Piston diameter: (psi) 6 inches 8 inches ΔP 10 12 14 16 10 12 14 16 5 80 96 112 128 142 170 199 227 10 160 192 224 256 284 341 398 454 15 240 287 335 383 426 511 596 681 20 319 383 447 511 568 681 795 909 DETAILS 25 399 479 559 639 710 852 994 1136 APPLICABLE IN 30 479 575 671 767 852 1022 1193 1363 THE FIELD 35 559 671 783 894 994 1193 1391 1590 40 639 767 894 1022 1136 1363 1590 1817 45 719 862 1006 1150 1278 1533 1789 2044 50 799 958 1118 1278 1420 1704 1988 2272

Well Tests

Prior to the Use of the Pumping Unit of the Invention:

The selected well had a production of 02 BO×0 BW, in October 2016, taking the following physical measurement:

Production before compressor Current production with compressor P Tbg P Csg P Tbg P Csg Incremental Compressor Well Oil Water (psi) (psi) Manometric Oil Water (psi) (psi) Manometric de Oil Suction Remark BMCG- 4453 2 0 10 3 10-280 psi/ 8 0 20-60 −4 20-300 psi/ 6 −4 psi Operating GMP-09 2 min 30 sec. compressor, 40 sec having no problem Total Production Increase 6

As it can be seen from the table above, the pressure without the compressor or pumping unit was 3 psi, changing to −4 (four negative) psi by using the compressor or pumping unit of the present invention, resulting consequently that, that difference of vacuum pressure allows a greater production.

Using the Pumping Unit of the Invention:

Fluid Dynamo- level metric Recom- Date Battery P_(Pipe) P_(Casing) Well details (FLAP) PPRL Torque card Remarks mendation Oct. 22^(nd), October 4537 10 @ 2.9 1374′ 36″ 3.58 24 1345′ 29′ 29′ 1,993 15,977 Card has Card has Decrease 2016 280 psi/ fluid fluid working 2′ pound. pound. time to 40″ 20 × 4.

One can remarkably observe an increase of the production from 2 BOPD to 8 BOPD, operating 24 hours under the same extraction conditions as those prior to the use of the pumping unit, thus obtaining better manometric tests.

In this way, the pumping unit for oil wells of the present invention is constituted and constructed, which is independent from the operation of the AIB rod pump and in turn, it allows the variation of the piston moving speed to extract a greater or lesser amount of gas in accordance with the existing pressure in the well annulus owing to the novel arrangement of the pressure transmitter and pressure switch. That is to say, the pressure is programmable, this being not possible with any conventional mechanism of the prior art. It is emphasized that the gas extraction cycle is continuous during the period of oil extraction.

Furthermore, some of the advantages of the unit of the present invention lie in:

The use of an external and independent pumping unit instead of a traditional reciprocating gas compressor CGBD (mechanical pumping), allows to further reduce gas pressure in the well annulus since its action is not limited by the geometry of the pumping rod unit, to the low GPM (<9), wherein independence of frequency of action of the pumping unit allows it to be smaller;

The pumping unit allows maintaining a constant gas pressure in the well, since it has the pressure switch and pressure transmitter that controls the piston speed according to the gas flow to be extracted, pressure being programmable;

Higher gas extraction capacity;

Increases production, with less flowing pressure;

Increase in recoverable reserves (vacuum in annulus);

Easy installation and transfer of the pumping unit;

It does not generate imbalance in alignment and balancing in a mechanical pumping unit;

Totally compact pumping unit (small dimensions) reducing the risk of accidents (there is no work at height);

Easy acquisition of spare parts;

Durability of materials used in its manufacture;

In case of maintenance of the compressor cylinder, it is replaced in approximately 30 minutes by another backup unit;

It is not necessary to stop the AIB rod pump;

The unit of the invention is environment friendly since it does not generate excessive noise;

It is not obstructive as it occupied little physical space in the well's location;

Compact compressor cylinder (fewer parts and flanges with uniform adjustment); improved metallurgy (high quality steel and aluminum), last generation seals (in stuffing box, flanges and piston)

Graphite Teflon seals for greater efficiency and durability;

Compressor accessories (horizontal check valves, bends, tee's, tubes, etc.) designed to work in media with gas flow;

Decrease in manufacturing cost; and

Longer useful life and efficiency of the pumping unit due to less maintenance and repairs, among many other advantages.

Thus, the invention allows varying the piston drive amount according to what we want by means of the variable speed drive that drives the motor and without depending on the frequency of actuation of the mechanical pumping as it occurs with the units of the prior art. In turn, the unit of the invention allows the compressor to be smaller since there being more frequency a smaller compressor is needed, thus allowing regulating the gas pressure of the well as desired owing to the arrangement of the pressure switch and pressure transmitter connected to the casing that, according to the desired programmed pressure, varies the speed of the motor that drives the compressor and therefore extracts more or less gas. 

I claim:
 1. A gas pumping unit for oil wells, wherein the pumping unit comprises: at least one compressor cylinder having at least one gas inlet in connection with the well, at least one gas outlet, one pivoting lower end and a double-acting piston having a drive shaft which is connected to a drive motor by means of a respective connecting rod, said drive motor being connected to a pressure transmitter operatively connected to a pressure switch which in turn is operatively connected to the well
 2. The gas pumping unit of claim 1, wherein the gas inlet comprises a lower gas inlet which is connected to a lower part of the compressor cylinder and an upper gas inlet which is connected to an upper part of the compressor cylinder, both lower and upper gas inlets being bifurcated and extending from a main gas inlet which is directly connected to the well through a respective conduit selected from the group consisting of a duct, pipe, hose and a combination thereof.
 3. The gas pumping unit of claim 2, wherein said gas outlet comprises a lower gas outlet which is connected to the lower part of the compressor cylinder and an upper gas outlet which is connected to the upper part of the compressor cylinder, both outlets extending and connecting to a main gas outlet.
 4. The gas pumping unit of claim 2, wherein the upper part of the compressor cylinder comprises an upper gas cylinder inlet/outlet which is connected to the upper gas inlet and upper gas outlet, while the lower part of the compressor cylinder comprises a lower gas cylinder inlet/outlet which is connected to the lower gas inlet and lower gas outlet.
 5. The gas pumping unit of claim 4, wherein between said upper and lower cylinder inlets/outlets and said upper and lower gas inlets/outlets, respective unidirectional check valves are arranged.
 6. The gas pumping unit of claim 1, wherein said drive motor is an electric motor connected to a reducer.
 7. The gas pumping unit of claim 1, wherein an upper end of the piston driving shaft has a connecting element provided with a bearing on which a connecting shaft is mounted.
 8. The gas pumping unit of claim 7, wherein said connecting rod is operatively connected to said connecting element by said connecting shaft.
 9. The gas pumping unit of claim 1, wherein said pivoting lower end comprises a lower arm provided with a bearing through which a shaft passes and this shaft has ends that are affixed to respective plates provided with bearings mounted in a frame.
 10. The gas pumping unit of claim 9, wherein the pumping unit is mounted on said frame. 